Creating consistent topology using PgRouting

Question

I'm developing an application that needs routing information for certain cities. First, I downloaded a openstreetmap datafile (*.osm) and then I imported it into a PostgreSQL database using osm2pgrouting tool (http://workshop.pgrouting.org/chapters/installation.html). After this, I have the following tables:

• nodes: that contains simple locations points
• ways: that contains ways with some nodes involved
• vertices_tmp: stores nodes that may be used for pgrouting funtcions like Djistra, A*...etc.

Would I use nodes that isn't in "vertices_tmp" table for calculate distances between nodes? Or I would only do it with the nodes stored in "vertices_tmp"?

Into ways table there are a field named "the_geom" that encapsulates different locations points (nodes). For example:

"MULTILINESTRING((1.5897786 42.5600441,1.5898376 42.5601455,1.589992 42.5605438,1.590095 42.5606795,1.5901782 42.5608026,1.5902238 42.561018,1.5902912 42.5616808,1.5903685 42.561899,1.5904008 42.5620563,1.5903836 42.5624117,1.5904265 42.5627151,1.5904947 42.5628368,1.5905981 42.5629553,1.5906926 42.5631007,1.590802 42.5633238,1.5908604 42.5634883,1.5909501 42.5637139,1.5910869 42.5638755,1.5913053 42.5639639,1.5914994 42.5640237,1.591648 42.5640261,1.5919232 42.5640145,1.5921124 42.5640363,1.5923292 42.5640953,1.592804 42.5643306))"

Can I route with intermediate nodes or only with source/target nodes?

My goal is to be able to routing betweent differents nodes or POIs, depending of its amenity tags, not only driving distance, walking distance too. Furthermore I need to calculate shortest path for source/targets nodes.

Any idea for do this?

Answer 1

For your routing topology the only "nodes" (or "vertices"), that matter, are the ones used in source and target column of your network table. vertices_tmp can be handy, but it's not required.

In general pgRouting functions take node ID's (you find all of them in vertices_tmp) as arguments, so using a point between source and target vertex is not possible with the "core" functions.

However, there is a number of "withPoints" functions, which exactly provide this extended functionality, see detailed explanation in https://docs.pgrouting.org/latest/en/withPoints-family.html#withpoints